CHAPTER XV.

_EXAMPLES IN ENGINE WORK._

In the figures from 308 to 328 inclusive are given three examples in engine work, all these drawings being from _The American Machinist_. Figures 308 to 314 represent drawings of an automatic high speed engine designed and made by Professor John E. and William A. Sweet, of Syracuse, New York. Figure 308 is a side and 309 an end view of the engine. Upon a bed-plate is bolted two straight frames, between which, at their upper ends, the cylinder is secured by bolts. The guides for the cross-head are bolted to the frame, which enables them to be readily removed to be replaned when necessary. The hand wheel and rod to the right are to operate the stop-cock for turning on and off the steam to the steam-chest.

The objects of the design are as follows: Figure 310 is a vertical section of the cylinder through the valve face, also showing the valve in section, and it will be seen that the lower steam passage enters the cylinder its full depth below the inside bottom, and that the whole inside bottom surface of the cylinder slopes or inclines towards the entrance of this passage. The object of this is to overcome the difficulty experienced from the accumulation of water in the cylinder, which, in the vertical engine, is usually a source of considerable annoyance and frequently the cause of accident.

Any water that may be present in the bottom finds its way by gravity to the port steam entrance, and is forced out by and with the exhaust steam at or before the commencement of the return stroke.

To assist in the escape of water from the top of the cylinder, the piston is made quite crowning at that end, the effect of which is to collect the water in a narrow band, instead of spreading it over a large surface. This materially assists in its escape, and at the same time presents a large surface for the distribution of any water that may not find its way out in advance of the piston.

The piston is a single casting unusually long and light, and is packed with four spring rings of 3/8 inch square brass wire.

The valve is a simple rectangular plate, working between the valve face and a cover plate, the cover plate being held in its proper position, relative to the back of the valve, by steam pressure against its outer surface, and by resting against loose distance pieces between its inner surface and the valve seat. This construction admits of the valve leaving the seat, if necessary, to relieve the cylinder from water, as in the instance of priming, and also, by the reduction of these pieces, admits of ready adjustment to contact, should it become necessary.

The cover plate is provided with recesses on its inner surface which exactly correspond with the ports in the valve face, and the corresponding ports and recesses are kept in communication with each other by means of relief passages in the valve. From this it will be seen that the valve is subjected to equal and balanced pressure on each of its sides, and hence, is in equilibrium.

The valve is operated through the valve motion, shown in Figure 311, the eccentric rod of which hooks on a slightly tapered block that turns on the pin of the rock arm, like an ordinary journal box.

The expansion, or cut-off, is automatically regulated by the operation of the governor in swinging the slotted eccentric in a manner substantially equivalent to moving it across the shaft, but is however favorably modified by the arrangement of the rock arm, which, in combination with the other motions, neutralizes the unfavorable operation of the usual shifting eccentric, and which, in connection with the large double port opening, provides for a good use of steam from 0 to 3/4 stroke.

The governor shown in Figure 312 is of the disc and single ball type, the centrifugal force of the ball being counteracted by a powerful spring. Friction is reduced to a minimum in the governor connection, by introducing steel rollers and hardened steel plates in such a manner as to provide rolling instead of sliding motion.

In order that a governor shall correctly perform its functions, it is unquestionably necessary that it have power largely in excess of the work required of it, and also that the friction shall represent a very low percentage of that power. In respect to this, especial means have been employed to reduce the friction; the valve being balanced, requires but little power to move it, while the governor ball being made heavy for the purpose of counterbalancing the weight of the eccentric and strap, its centrifugal force when the engine is at full speed is enormous, the spring to counteract it having to sustain from _two to three thousand pounds_. Under these circumstances, as might be expected, the regulation is remarkably good. This is a very important consideration in an engine working under the conditions of a roll-train engine.

Figure 313 represents a section of the pillow block box, crank-pin and wheel, together with the main journal. It will be seen that the end of the box next the crank wheel has a circular groove around its outside, and that a corresponding groove in the crank wheel projects over this groove. From this latter groove an oil hole of liberal size extends, as shown, to the surface of the crank-pin. Any oil placed at the upper part of the groove on the box finds its way by gravity into the groove in the crank wheel, and is carried by centrifugal force to the outside surface of the crank-pin; so that whatever other means of lubrication may be employed, this one will always be positive in its action. This cut also shows the manner in which the box overlaps the main journal and forms the oil reservoir.

Another feature in the construction of this box is the means by which it is made to adjust itself in line with the shaft. It will be observed that it rests on the bottom of the jaws of the frame on two inclined surfaces, which form equal angles with the axis of the shaft when in its normal position, and that by moving longitudinally in either direction, as may be necessary, the box will accommodate itself to a change in the alignment of the shaft. In order that it may be free to move for this purpose it is not fitted with the usual fore and aft flanges. By this means any slight derangement, as in either the outboard or inboard bearing wearing down the fastest, is taken care of, the movement of the box on the inclined surfaces being for this purpose equivalent to the operation of a ball and socket bearing.

Figure 314 gives a side and an edge view of the connecting rod, the rod being in section in the edge view, and the brasses in section lined in both views.

The cross-head pin, it will be observed, is tapered, and is drawn home in the cross-head by a bolt; the sides of the pin are flattened somewhat where the journal is, so that the pin may not wear oval, as it is apt to do, because of the pull and thrust strain of the rod brasses falling mainly upon the top and bottom of the journal, where the most wear therefore takes place. The brasses at the crossed end are set up by a wedge adjustable by means of the screw bolts shown. The cross-head wrist pin being removable from the cross-head enables the upper end of the rod to have a solid end, since it can be passed into place in the crossed and the wrist pin inserted through the two. The lower ends of the connecting-rod and the crank-pin possess a peculiar feature, inasmuch as by enlarging the diameter of the crank-pin, the ends of the brasses overlap, to a certain extent, the ends of the journal, thus holding the oil and affording increased lubrication. The segments that partly envelop the cross-head pin and crank-pin, and are section lined in two directions, producing crossing section lines, or small squares, show that the brasses are lined with babbitt metal, which is represented by this kind of cross-hatching. These drawings are sufficiently open and clear to form very good examples to copy and to trace on tracing paper.

Figures 315, 316 and 317 represent, in place upon its setting, a 200 horse-power horizontal steam-boiler for a stationary engine, and are the design of William H. Hoffman. The cross-sectional view of the boiler shell in Figure 315 shows the arrangement of the tubes, which, having clear or unobstructed passages between the vertical rows of tubes, permits the steam to rise freely and assists the circulation of the water. The dry pipe (which is also shown in Figure 316) is a perforated pipe through which the steam passes to the engine cylinder, its object being to carry off the steam as dry as possible; that is to say, without its carrying away with the steam any entrained water that may be held in suspension. Figure 316 is a side elevation with the setting shown in section, and Figure 317 is an end view of the boiler and setting at the furnace end. The boiler is supported on each side by channel iron columns, these being riveted to the boiler shell angle pieces which rest upon the columns. The heat and products of combustion pass from the furnace along the bottom of the boiler, and at the end pass into and through the tubes and thence over the top of the boiler to the chimney flue. There is shown in the bridge wall an opening, and its service is to admit air to the gases after they have passed the bridge wall, and thus complete the combustion of such gases as may have remained unconsumed in the furnace. The cleansing door at one end and that lined with asbestos at the other, are to admit the passage of the tube cleaners. The asbestos at the top of the boiler shell is to protect it from any undue rise in temperature, steam being a poorer conductor of heat than water, and it being obvious that if one side of the boiler is hotter than the other it expands more from the heat and becomes longer, causing the boiler to bend, which strains and weakens it. The sides of the setting are composed of a double row of brick walls with an air space of three inches between them, the object being to prevent as far as possible the radiation of heat from the walls. The brick-staves are simply stays to hold the brick work together and prevent its cracking, as it is apt, in the absence of staying, to do.

Figures from 318 to 330 are working drawings of a 100-horse engine, designed also by William H. Hoffman.

Figure 318 represents a plan and a side view of the bed-plate with the main bearing and the guide bars in place. The cylinder is bolted at the stuffing box end to the bed-plate, and is supported at the outer end by an expansion link pivoted to the bed-plate. The main bearing is provided with a screw for adjusting the height of the bottom piece of the bearing, and thus taking up the wear. The guide bars are held to the bed in the middle as well as at each end.

Figures 319 and 320 represent cross sections of the bed-plate.

Figure 321 represents a side elevation of the cylinder, and Figure 322 an end view of the same, the expansion support being for the purpose of permitting the cylinder to expand and contract under variations of temperature without acting to bend the bed-plate, while at the same time the cylinder is supported at both ends. The cylinder and cylinder covers are jacketted with live steam in the steam-spaces shown.

A view of the steam-chest side of the cylinder is given in Figure 323, and a horizontal cross section of the cylinder, the steam-chest and the valves, is shown in Figure 324. The main valves are connected by a right and left hand screw, to enable their adjustment, as are also the cut-off valves.

Figures 325 and 326 show the cam wrist plate and the cut-off mechanism. The cam wrist plate, which is of course vibrated by the eccentric rod, has an inclined groove, whose walls are protected from wear by steel shoes. In this groove is a steel roller upon a pin attached to the bell crank operating the main valve stem. The operation of the groove is to accelerate the motion imparted from the eccentric to the valve at one part of the latter's travel, and retard it at another, the accelerated portion being during the opening of the port for steam admission, and during its closure for cutting off, which enables the employment of a smaller steam-port than would otherwise be the case.

The shaft for the cam plate is carried in a bearing at one end, and fits in a socket at the other, the socket and bearing being upon a base plate that is bolted to the bed-plate of the engine; a side view of the construction being shown in Figure 327.

Figure 328 represents the cross-head, whose wrist pin is let into the cross-head cheeks, so that it may be removed to be turned up true. The clip is to prevent the piston rod nut from loosening back of itself.

Figure 329 represents a side view; and Figure 329 _a_ a section through the centre of the eccentric and strap.

The eccentric is let into the strap and is provided with an eye to receive a circular nut by means of which the length of the eccentric rod may be adjusted, a hexagon nut being upon the other or outer end of the eye.

Figure 330 shows the construction of the connecting rod, the brasses of which are adjustable to take up the wear and to maintain them to correct length, notwithstanding the wear, by means of a key on each side of each pair of brasses, the keys being set up by nuts and secured by check nuts.

INDEX.

Ames' lathe feed motion, drawing a part of, 208.

Angle of three lines, one to the other, to find, 55, 56. of two lines, one to the other, to find, 54, 55, 56.

Angles, acute and obtuse, 57.

Arc of a circle, an, 50.

Arcs, construction with four, 67, 68.

Arcs for the teeth of wheels, to draw, 205.

Arrangement of different views, 94-111.

Automatic high speed engine, drawings of, 289.

Axis of a cylinder, 51. of an ellipse, 63.

Ball or sphere, representation of by line-shading, 87, 88.

Bed-plate, cross section of, 299. plan and side view of, with main bearing and guide bars, 299.

Bell-mouthed body, representation of by line-shading, 88, 89.

Bevelled gear, one-half of, and an edge view projected from the same, 207. one of which is line-shaded, 210. wheels, 203.

Bevelled gears, small, 208.

Bevelled wheels, a pair of, in section, 208.

Bisected line, 50.

Black lines of a drawing, how to produce, 32.

Blacksmith, drawings for the, 172.

Blake's patent direct acting steam pump, 284, 285.

Boiler drilling machine, a, 269, 270.

Boiler, end view of, 297. shell, sectional view of, 296.

Bolt heads and nuts, United States standard, 114, 118. to draw a square-headed, 125. with a hexagon head, to draw. 113, 114. with a square under the head, 149.

Bolts and nuts, dimensions of United States standard, 117. United States standard, forged or unfinished, 116.

Bolts, nuts and polygons, examples in, 112-151.

Bow pen, applying the ink to, 46. large, with a removable leg, 22.

Brass, representation of, by cross-hatching, 82.

Bread for rubbing out, 26.

Bristol board, use of rubber on, 26.

Brush-shading, 281.

Brushes, size and use of, 280.

Cam, a, and a lever arm in one piece on a shaft, a shoe sliding on the line, and held against the cam face by the rod, to find the position of the face of the shoe against the cam, 228. a full stroke, method of drawing or marking out, 237-241. designed to cut off steam at five-eighths of the piston stroke, 244-246. heart, to draw, 75, 76. object of using, instead of eccentric, 234.

Cam wrist plate, and cut-off mechanism, 301.

Cams, cut-off, employed instead of eccentrics on steamboats, examples in drawing, 232. finding the essential points of drawings of, 241-244. necessary imperfections in the operations of, 247-249. part played by the stroke of the engine in determining the conformation of, 241. three-fourths and seven-eighths, 246, 247.

Cap nut, to pencil in a, 143.

Cast iron, representation of, 277. representation of by cross-hatching, 82.

Centre from which an arc of a circle has been struck, to find, 52.

Centre of a circle, 51.

Centre punch in which the flat sides run out upon a circle, the edges forming curves, 150.

Chamfer circles of bolt heads, 120-123. of Franklin Institute bolt head, 119.

Chord of an arc, 50.

Chuck plate with six slots, to draw, 131.

Circle, degrees of a, 52-55. pencil and circle pen, use of, 43, 44. pens, 37, 38. that shall pass through any three given points, to draw, 51. to divide into six divisions, 56, 57.

Circles, to divide with the triangle, 129. for bolt heads, to draw, 128. German instrument for drawing, 44, 45. use of the instrument in forming, 42-45.

Circular arcs, Rankine's process for rectifying and subdividing, 210.

Circumference, 50.

Collar, a representation of, 96.

Coloring and shading, points to be observed in, 278.

Color, to maintain an even shade of, 278.

Colors, mixing, 278.

Condenser, independent, 288.

Cone, cylinder intersecting a, 186.

Connecting rod, 169, 295, 303. drawing representing the motion which a crank imparts to a, 249, 250. end, 147.

Copper, representation of, 277.

Corner where the round stem meets the square under the head, 150.

Coupling rod, working drawings of a, 169.

Crank, drawing representing the motion which it imparts to a connecting rod, 249. pin and wheel, 294.

Cross-hatching or section lining, 77-82. made to denote material of which the piece is composed, 81, 82. may sometimes cause the lines of the drawing to appear crooked to the eye, 80, 81. representation by, of a section of a number of pieces one within the other, the central bore being filled with short plugs, 78, 79. representation by, of three pieces put together, having slots or keyways through them, 79, 80. the diagonal lines in, should not meet the edges of the piece, 78.

Cross-head, 301.

Cross, use of, to designate a square, 95, 96.

Cube, with a hole passing through it, to draw, 101, 102.

Cupped ring, representation of, 98.

Curved outline, representation of, 86, 87.

Curve for tooth face, how to find, 198. representation of the radius for, 87.

Curves and lines, 48-76. of gear teeth, names of, 193.

Curves for moulding cutter, to find the, 257-263. of thread, template for drawing, 165. of wheels, construction, to find, 204. screw threads, drawing, 159. templates called, 21. use of, in practice, 21.

Cut-off cams, employed instead of eccentrics on steamboats, examples in drawing, 232. manner of finding essential points of drawings of, 241-244. necessary imperfections in the operations of, 247-249. part played by the stroke of the engine in determining the conformation of, 241.

Cut-off mechanism, 301.

Cutting tool for a planing machine, representation of, 264-266.

Cylinder, 299. a solid, representation of, 94, 95. intersecting a cone, 186 of an engine, 299-301. of an engine, drawing of, 289.

Cylindrical body joining another at a right angle, a, 180. body whose top face, if viewed from one point, would appear as a straight line, or if from another as a circle, 188. piece of wood, which is to be squared, and each side of which square must be an inch, to find the diameter, 136. pieces and cubes, representation of, 95. pieces, representation of, by cross-hatching, 77, 78.

Cylindrical pieces, representation of three, one within the other, by cross-hatching, 78. pieces that join each other, representation of, 86. pin line-shaded, representation of, 86.

Decagon, a, 63.

Degrees of a circle, 52-55.

Diameter of a cylindrical piece of wood, which is to be squared, and each side of which square must measure an inch, to find, 136.

Diamond, a, 59, 60.

Different views, arrangement of, 94-111.

Dimension figures in mechanical drawing, 91.

Dimensions, marking, 91-93.

Distances, relative from the eye, representation of, by line-shading, 89.

Dodecagon, a, 63.

Dotted lines, use of, 48.

Double eye, or knuckle-joint, pencil lines for, 146. or knuckle-joint, with an offset, 147.

Double thread, 156.

Drawing board, 17, 18. fastening the drawing to, 278. size of, 18. small, advantage of, to student, 18.

Drawing for engraver on wood, 268. gear wheels, 193-222.

Drawing instruments, 22-26. parts of, 34. selecting and testing, 22.

Drawing paper, 26-29. different qualities, kinds and forms, 26, 27. location of on the drawing board, 28, 29.

Drawing the curves for screw threads, 159. to scale, making a, 177.

Drawings for engraving, necessity of conforming to the particular process of, 266. for engravings by the wax process, 268, 269.

Drawings for photo-engraving, 266. for the blacksmith, 172. shading and coloring, 277-288.

Drilling machine, a boiler, 269, 270.

Eccentric and strap, 301. to find how much motion it will give to its rod, 223.

Edge view of a wheel, to draw, 203.

Elevation, 94.

Ellipse, dimensions of, how taken and designated, 63. form of a true, 66. most correct method of drawing, 72. the, 63-75.

Elliptical figure, whose proportion of width to breadth shall remain the same, whatever the length of the major axis, 69.

Emery paper, use of on the lining pen, 37.

Ennagon, a, 62, 63.

Engine work, examples of, 289-303.

Engine, working drawings of a 100 horse-power, 299.

Engravings by the wax process, drawings for, 268, 269.

Examples for practice, 169-177 in bolts, nuts and polygons, 112-151. of engine work, 289-303. of work with nine sides, 135.

Feed motion of a Niles horizontal tool work boring mill, 209.

Five-sided figure, to draw, 132, 133.

Flanks of teeth to trace hypocycloides, for, 200.

Foci of an ellipse, 64.

Franklin Institute or United States Standard for heads of bolts and of nuts, basis of, 118.

Full stroke cam, method of drawing or marking out a, 237-241.

Gear, part of, showing the teeth in, the remainder illustrated by circles, 209.

Gear teeth, names of the curves and lines of, 193.

Gear wheels, drawing, 193-222. various examples for laying out, 214-222.

Gearing oval, construction of, 210.

General view, 94.

Geometrical terms, simple explanation of, 48.

Geometry, advantage of to the draughtsman, 48.

Governor of an engine, 292, 293.

Guide bolts from one pulley to another, arrangement of idle pulleys to, 264.

Heart cam, to draw, 75, 76.

Hexagon, a, 62, 63. head, representation of a piece with, 96. head, to draw the end view of, 125, 126, 127. headed screw, to draw, 113, 114. radius across corners, 138.

Hexagonal form, representation of, 98. or hexagon heads of bolts, 118, 119.

Hole, representation of by shade or shadow line, 83.

Hollows in connection with round pieces, representations of, 87-89.

Hypocycloides for the flanks of teeth, to trace, 200.

Independent condenser, 288.

India ink, advantages of in drawing, 30. difference between good and inferior, 31. good, characteristics of, 31.

India ink, Higgins', 30. mixing, 25. testing, 31, 32. the two forms of, 30. to be used thick, 32. use of, 30. use of on parchment, 32.

Ink, applying, to the bow pen, 46. for drawing, 30-33.

Instruments, preparation and use of, 34-47.

Iron planing machine, representation of, 282.

Iron, wrought and cast, representation of by cross-hatching, 82.

Journal, 294.

Journals of shafts, 277.

Key, a, drawn in perspective, 92, 93. drawing of a, 91. marking the dimensions of on a drawing, 92. representation of with a shade line, 84.

Knuckle-joint, pencil eye for, 146. with an offset, 147.

Large bow or circle pen, joints of, 23.

Lathe centre, representation of, 86.

Lathe feed motion, drawing of a part of a, 208.

Lead pencils for drawing, 23.

Lead, representation of by cross-hatching, 82.

Left-hand thread, 156.

Lever, a, actuating a plunger in a vertical line, to find how much a given amount of motion of the long arm will actuate the plunger, 226. and shaft, drawing, 103, 104, 105. arm and cam, in one piece on a shaft, a shoe sliding on the line, and held against the cam face by the rod, to find the position of the face of the shoe against the cam, 228. example of the end of a, acting directly on a shoe, 225. to find how much a given amount of motion of a long arm will move the short arm of a lever, 224.

Levers, two, upon their axles or shafts, the arms connected by a link, and one arm connected to a rod, 227.

Light in shading, 280. management of, in mechanical drawing, 82, 83.

Line-shaded engravings, drawing for, 264-276.

Line-shading, 77-90. and drawing for line-shaded engravings, 264-276. in perspective drawing of a pipe-threading stock and die, 85. mechanical drawing made to look better and show more distinctly by, 82. simplest form of, 82.

Lines and curves, 48-76.

Lines in pencilling, where to begin, 24, 25.

Lining pen, 22.

Lining pen, form of, 34-37.

Lining pen, use of with a T square, 45, 47.

Link introduced in the place of a roller, to find the amount of motion of the rod, 226. quick return, plotting out the motion of a shaper, 250-253.

Links, pencilling for, 145, 146.

Locomotive frame, 174. spring, 169.

Machine screw, to draw, 112, 113.

Main journal, 294.

Marking dimensions, 91-93.

Measuring rules, draughtsman's, 33.

Mechanical motions, plotting, 223-263.

Motion an eccentric will give to its rod, to find, 223. a shaper link, quick return, plotting out, 250-253. imparted in a straight line to a rod, attached to an eccentric strap, to find the amount of, 229-231. which a crank imparts to a connecting rod, 249, 250.

Motions, plotting mechanical, 223-263.

Moulding cutter, finding the curves for, 257-263.

Niles' horizontal tool work boring mill, feed motion of a, 209.

Nonagon, a, 62.

Nut, a representation of the shade line on, 84. cap, to pencil in a, 145. to show the thread depth in the top or end view of a, 166.

Nuts' and bolts, dimensions of United States Standard, 117.

Nuts and polygons, examples in, 112-151.

Octagon, a, 62, 63.

Oil cup, representation of, 282, 284.

Outline views, 97, 98.

Oval gearing, construction of, 210.

Paper cutter, the form of the end of, 25. rules or scales, 32.

Parabola, to draw by lines, 74, 75. to draw mechanically, 73, 74.

Parallel lines, 49.

Parallelogram, 59, 60.

Parchment, use of India ink on, 32.

Pen, German, regulated to draw lines of various breadths, 84, 85. lining, form of, 34-37.

Pen point, forming the, 39, 40. form of recently introduced, 39.

Pen points, oil-stoning, 36.

Pen, with sapphire points, 85.

Pens, circle, 37, 38. used in drawing, 22.

Pencil holders for sticks of lead, 24. lines in drawing, 23. sharpening for fine work, 24.

Pencilling for a link, having the hubs on one side only, 145. in a cap nut, 145.

Penknife and rubber scratching out, 25.

Pentagon, a, 62, 63.

Perimeter, the, 50.

Periphery, 50.

Perpendicular line, 49.

Perspective sketches to denote the shape of the piece, 93.

Photo-engraving, drawings for, 266, 267.

Piece of work should, in mechanical drawing, be presented in as few views as possible, 94.

Pillow block box, 294.

Pin, in a socket, in section, representation of, 87, 88.

Pinion teeth, to draw to the pitch of the inner and small end of, 206.

Pins and discs, discrimination of, in mechanical drawing, 96.

Pipe threading stock and die, drawing of, 85.

Pitch circle of the inner and small end of, to draw, 206. to obtain a division of the lines that divide, 167.

Plan, 94.

Planing machine, a cutting tool for, 264-266.

Plotting mechanical motions, 223-263. out the motion of a shaper link quick return, 250-253.

Point, a, 49.

Points of drawing instruments, 34.

Polished surfaces, to show by shading, 282.

Polygon of twelve equal sides, to draw, 129, 130.

Polygons, bolts and nuts, examples of, 112-151. construction of, 61. designation of the angles of, 62. names of regular, 62, 63. scales giving the lengths of the sides of, 135.

Preparation and use of the instruments, 34-47.

Produced line, 50.

Projecting one view from another, 106.

Projections, 178-192.

Protractors, 53.

Pulley, Medart, shading a, 280.

Pulleys, arrangement of idle, to guide bolts from one pulley to another, 264.

Quadrangle, quadrilateral or tetragon, 59.

Quadrant of a circle, 50.

Quick return motion, Whitworth, plotting out, 253-256.

Radius across corners of a hexagon, 138.

Rankine's process for rectifying and subdividing circular arcs, 210.

Reducing scales, 175.

Rectangle, a, 59, 60.

Rectangular piece, a, to draw in two views, 98, 99. requires two or three views, 96, 97. representation of, 96.

Red ink, marking dimensions of mechanical drawings in, 91.

Rhomboid, a, 60.

Rhomb, rhombus or diamond, 54, 60.

Right line, a, 49.

Ring with a hexagon cross section, 98.

Rivet, side and end views of, 49.

Roller, example of a short arm having a, acting upon a larger roller, 225.

Rod, attached to an eccentric strap, to find the amount of motion imparted in a straight line to a, 229-231. end with a round stem, 148.

Round stem, a representation of, 96. top and bottom thread, 156.

Rubber, 25. form of, 26. proper uses of, 25. sponge, 26. the use of, 25. to be used on Bristol board, 26. velvet, 26.

Rule, steel, 32.

Sapphire points, pen with, 85.

Scale for diameter of a regular polygon, 140. of tooth proportions, 195. triangular, 33.

Scales, for measurement and drawing, 32. reducing, 175.

Scratching out, 25.

Screw machine, to draw, 112, 113. thread, United States standard, to draw, 159-160. threads and spirals, 152-168. threads, drawing the curves for, 159. threads for small bolts, with the angles of the threads drawn in, 152-155.

threads of a large diameter, 156.

Section lining or cross-hatching, 77-82.

Sectional view of a section of a wheel, for showing dimensions through arms and hub, 202.

Sector of a circle, 51.

Segment of a circle, 50.

Semicircle, 51.

Shade curve, representation of, 87. line produced for circles, 84.

Shade line, produced in straight lines, 84. or shadow line, 82.

Shading a Medart pulley, 280. and coloring, points to be observed in, 278. brush, 281. by means of lines to distinguish round from flat surfaces, and denote relative distances of surfaces, 85. example in, of a Blake's patent direct acting steam pump, 284, 285. example of, in an independent condenser, 288. light in, 280. simple, 277. to show by, that the surfaces are highly polished, 282.

Shadow line, 82. lines and line shading, 77-90.

Shaft for cam plate, 301.

Shaper link, quick return, plotting out the motion of a, 250-253.

Shoe against a cam, to find the position of the face of, 228.

Side elevation, drawing a, 106.

Sides or flats of work, to find the lengths of, 135, 136.

Slots not radiating from a centre, to draw, 131, 132. radiating from a centre, 131.

Spiral spring, to draw, 166.

Spiral wound round a cylinder, whose end is cut off at an angle, 178.

Spirals and screw threads, 152-168.

Sponge, rubber, 26.

Spring bow pencil, for circles, 22. pen, for circles, 22, 23.

Spring, spiral, to draw, 166.

Spur wheel teeth, how to draw, 194.

Square, a, 59, 60. body, which measures one inch on each side, to find what it measures across the corners, 136.

Square part, a representation of, 96. parts, use of a cross to designate, 95, 96. thread, to draw a, 162-164.

Steam boiler, horizontal, for stationary engine, 296. chest and valves, 301. chest side, and horizontal cross section of cylinder, 301. pump, Blake's patent direct acting, 284, 285.

Steel, representation of, 277. representation of by cross-hatching, 82. square, improved, with pivoted blade, 19.

Steps, to draw a piece containing, 99-101.

Stock and die, pipe-threading, drawing of, 85.

Straight line in geometry termed a right line, 49. or lining pen, use of with a T square, 45, 47.

Stud, to draw a, 142.

Stuffing-box and gland, 169.

Surface of the paper, condensing after rubbing out, 25.

Surfaces, highly polished, to show by shading, 282.

Tacks for drawing paper, 27, 28.

Tangent, 51.

Taper or conical hole, to denote in drawing, 102. sides in a drawing, 102, 103.

Tees, 180.

Teeth of wheels, rules for drawing, 203. pinion, to draw the pitch of the inner and small end of, 206. spur wheel, how to draw, 194. to trace hypocycloides for the flanks of, 200.

Template for drawing the curves of thread, 165.

Templates called curves, 21.

T square, 18, 19.

T squares, different kinds of, 19.

Tetragon, a, 59, 62, 63.

Thread, a double, 156. a round top and bottom, 156. depth in the top or end view of a nut, to show, 166. left hand, 156. square, to draw a, 162-164. Whitworth, 156.

Threads of a large diameter, 156.

Thumb tacks for drawing paper, 27.

Tint, to graduate the depth of, for a cylindrical surface, 279.

Tooth face, how to find the curve for, 198. proportions, Willis' scale of, 195.

Tracing cloth, 29. paper, 29.

Trammel, use of in drawing an ellipse, 72.

Trapezium, 60.

Trapezoid, a, 60.

Triangle, equilateral, 58, 59. isosceles, 58, 59. obtuse, 58. right angle, 58. scalene, 59. use of in dividing circles, 129. use of in drawing polygons, 129, 130. use of to draw slots radiating from a centre, 131.

Triangles, 19-21, 58-60. requirements in use of, 20, 21. to draw, 133. using with the square, 20.

Triangular scale, 33.

Trigon, a, 62, 63.

True ellipse, a near approach to the form of, 69-72.

United States standard bolts and nuts, 114-118. standard thread, to draw, 159, 160.

Valve of an engine, 290-292.

Valves, 301.

Vertex, the, 59.

Views, different arrangement of, 94-111. of a piece of work, designations of, 103, 104. of a piece, two systems of placing, 106-111.

Washer, a, representation of the shadow side of, 83.

Wax process, drawings for engravings by, 268, 269. engraving from a print from a wood engraving, 269.

Wedge-shaped piece, representation of a, 97.

Wheel, edge view of a, to draw, 203. sectional view of a section of a, 202.

Wheels, construction, to find the curves of, 204. to draw the arcs for the teeth of, 205.

Whitworth thread, 156. quick return motion, plotting out, 253-256.

Willis' scale of tooth proportions, 195. application of, 197.

Wood engraving, drawing for, 268.

Wood, representation of by cross-hatching, 82. representation of, regular and irregular shade lines in, 90.

Wrought iron, representation of, 277. representation of by cross-hatching, 82.

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